Thermally curable binding agents

ABSTRACT

A heat-curable binder based on an aqueous polymer dispersion comprising an emulsion polymer (EP), a polymer composed of at least 5% by weight of an ethylenically unsaturated monocarboxylic acid, dicarboxylic acid or dicarboxylic anhydride (acid polymer SP for short), and monofunctional or polyfunctional epoxide compounds as curatives. The monofunctional or polyfunctional epoxide compound is stirred, preferably in the liquid state, into the aqueous polymer dispersion. Besides the epoxide compound, the heat-curable binder may further comprise a polyol or an alkanolamine as hardener.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat-curable binder based on anaqueous polymer dispersion comprising

-   -   an emulsion polymer (EP),    -   a polymer composed of at least 5% by weight of an ethylenically        unsaturated monocarboxylic acid, dicarboxylic acid or        dicarboxylic anhydride (acid polymer SP for short), and    -   monofunctional or polyfunctional epoxide compounds as curatives.

The present invention further relates to a process for preparing theheat-curable binders based on an aqueous polymer dispersion and to theiruse as binders for moldings or nonwovens formed from fibrous orparticulate materials.

2. Description of the Background

Heat-curable binders formed from polycarboxylic acids and polyols and/oralkanolamines are known, for example, from EP-A 445578, EP-A 583086,EP-A 882074, EP-A 882093 or DE-A 19949592.

EP-A 882074 and DE-A 19949592 specify, inter alia, alkoxysilanes aspossible additives and curatives for such binders. As further additivesand curatives for binders formed from polycarboxylic acids and polyols,EP-A 445578 discloses, inter alia, polyfunctional amines.

EP-A 576 128 describes adhesive compositions which comprise an acid-richpolymer component and a low-acid polymer component. The acid-richpolymer component is based on a monomeric mixture of from 40 to 95% ofan alkyl acrylate or methacrylate and from 5 to 60% of an ethylenicallyunsaturated acid, such as acrylic acid or methacrylic acid. The low-acidpolymer component is based on a monomer mixture of from 90 to 100% of analkyl acrylate or alkyl methacrylate and from 0 to 10% of anethylenically unsaturated acid. The composition is prepared by aqueousemulsion polymerization, the acid-rich polymer component beingpolymerized in the presence of the low-acid polymer component or viceversa. The pH of the composition is adjusted to the desired level byadding ammonium hydroxide or sodium hydroxide. The composition can beused as a pressure sensitive adhesive, laminating adhesive, adhesive fortextiles, nonwovens, and packaging, and as wood glue.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide heat-curable binderswhich are an improvement on the existing heat-curable binders and whichare suitable, among other things, for significantly increasing thestrength of the moldings obtained from them, and which feature asignificantly reduced water absorption and solvent absorption and alsohave significantly decreased leaching losses. At the same time thebinders of the invention are to be obtainable by an extremely simple andeconomic process and are to have an extremely low curing temperature.

The invention accordingly provides a heat-curable binder based on anaqueous polymer dispersion comprising

-   -   an emulsion polymer (EP),    -   a polymer composed of at least 5% by weight of an ethylenically        unsaturated monocarboxylic acid, dicarboxylic acid or        dicarboxylic anhydride (acid polymer SP for short), and    -   monofunctional or polyfunctional epoxide compounds as curatives.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention further provides a process for preparing the heat-curablebinders of the invention, and also provides for their use as binders formoldings or nonwovens formed from fibrous or particulate materials.

The emulsion polymer (EP) is preferably composed of at least 40% byweight, with particular preference at least 60% by weight, with veryparticular preference at least 80% by weight, of what are known asprincipal monomers.

The principal monomers are selected from C₁-C₂₀ alkyl (meth)acrylates,vinyl esters of carboxylic acids containing up to 20 carbon atoms,vinylaromatics having up to 20 carbon atoms, ethylenically unsaturatednitrites, vinyl halides, vinyl ethers of alcohols containing 1 to 10carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or2 double bonds, and mixtures of these monomers.

Examples include alkyl (meth)acrylates having a C₁-C₁₀ alkyl radical,such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethylacrylate, and 2-ethylhexyl acrylate.

In particular, mixtures of the alkyl (meth)acrylates are also suitable.

Vinyl esters of carboxylic acids having from 1 to 20 carbon atoms are,for example, vinyl laurate, vinyl stearate, vinyl propionate, Versaticacid vinyl esters, and vinyl acetate.

Suitable vinylaromatic compounds include vinyltoluene, α- andp-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene,and, preferably, styrene. Examples of nitriles are acrylonitrile andmethacrylonitrile.

The vinyl halides are chloro-, fluoro- or bromo-substitutedethylenically unsaturated compounds, preferably vinyl chloride andvinylidene chloride.

Examples of vinyl ethers include vinyl methyl ether and vinyl isobutylether. Preference is given to vinyl ethers of alcohols containing 1 to 4carbon atoms.

Hydrocarbons having 2 to 8 carbon atoms and two olefinic double bondsinclude butadiene, isoprene, and chloroprene, those containing onedouble bond, for example, ethylene or propylene.

Preferred principal monomers are the C₁ to C₁₀ alkyl acrylates andmethacrylates, especially C₁ to C₈ alkyl acrylates and methacrylates.Also suitable, preferably, are mixtures of C₁-C₁₀ alkyl acrylates orC₁-C₁₀ alkyl methacrylates with vinylaromatics, especially styrene.

Very particular preference is given to methyl acrylate, methylmethacrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octylacrylate, and 2-ethylhexyl acrylate, styrene, and mixtures of thesemonomers.

Besides the principal monomers the free-radically polymerized polymermay contain further monomers, e.g., monomers containing carboxylic acid,sulfonic acid or phosphonic acid groups. Carboxylic acid groups arepreferred. Examples that may be mentioned include acrylic acid,methacrylic acid, itaconic acid, maleic acid, and fumaric acid.

Further monomers are also, for example, hydroxyl-containing monomers,especially C₁-C₁₀ hydroxyalkyl (meth)acrylates, such as hydroxyethylacrylate, for example, and also (meth)acrylamides.

More further monomers that may be mentioned include phenyloxyethylglycol mono(meth)acrylate, glycidyl acrylate, glycidyl methacrylate, andamino (meth)acrylates such as 2-aminoethyl (meth)acrylate.

Crosslinking monomers are among other further monomers that may bementioned.

Moreover, mention may also be made of monomers containing hydrolyzableSi groups.

The fraction of monomers containing carboxylic acid groups or carboxylicanhydride groups is generally less than 10% by weight, in particularless than 5% by weight, based on EP.

EP is prepared by emulsion polymerization.

For the emulsion polymerization it is possible to use ionic and/ornonionic emulsifiers and/or protective colloids or stabilizers assurface-active compounds.

A detailed description of suitable protective colloids is given inHouben-Weyl, Methoden der organischen Chemie, Volume XIV/1,Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 411 to420. Suitable emulsifiers include anionic, cationic, and nonionicemulsifiers. As accompanying surface-active substances it is preferredto use exclusively emulsifiers, whose molecular weights, unlike those ofthe protective colloids, are normally below 2000 g/mol. In the casewhere mixtures of surface-active substances are used, the individualcomponents must of course be compatible with one another, somethingwhich can be checked in case of doubt by means of a few preliminarytests. It is preferred to use anionic and nonionic emulsifiers assurface-active substances. Examples of customary accompanyingemulsifiers are ethoxylated fatty alcohols (EO units: 3 to 50, alkyl: C₈to C₃₆), ethoxylated mono-, di- and trialkylphenols (EO units: 3 to 50,alkyl: C₄ to C₉), alkali metal salts of dialkyl esters of sulfosuccinicacid, and also alkali metal salts and ammonium salts of alkyl sulfates(alkyl: C₈ to C₁₂), of ethoxylated alkanols (EO units: 4 to 30, alkyl:C₁₂ to C₁₈), of ethoxylated alkylphenols (EO units: 3 to 50, alkyl: C₄to C₉), of alkylsulfonic acids (alkyl: C₁₂ to C₁₈), and ofalkylarylsulfonic acids (alkyl: C₉ to C₁₈).

Further suitable emulsifiers are compounds of the formula I

in which R⁵ and R⁶ are hydrogen or C₄ to C₁₄ alkyl and are notsimultaneously hydrogen, and X and Y may be alkali metal ions and/orammonium ions. Preferably, R⁵ and R⁶ are linear or branched alkylradicals having 6 to 18 carbon atoms or hydrogen and in particular have6, 12 and 16 carbon atoms, R⁵ and R⁶ not both simultaneously beinghydrogen. X and Y are preferably sodium, potassium or ammonium ions,with sodium being particularly preferred. Particularly advantageouscompounds I are those in which X and Y are sodium, R⁵ is a branchedalkyl radical having 12 carbon atoms, and R⁶ is hydrogen or R⁵. It iscommon to use technical-grade mixtures containing from 50 to 90% byweight of the monoalkylated product, an example being Dowfax® 2A1 (trademark of the Dow Chemical Company).

Suitable emulsifiers are also given in Houben-Weyl, Methoden derorganischen Chemie, Volume 14/1, Makromolekulare Stoffe, Georg ThiemeVerlag, Stuttgart, 1961, pages 192 to 208.

Examples of emulsifier trade names include Dowfax® 2A1, Emulan® NP 50,Dextrol® OC 50, Ermulgator 825, Emulgator 825 S, Emulan® OG, Texapon®NSO, Nekanil® 904 S, Lumiten® I-RA, Lumiten E 3065, Disponil FES 77,Lutensol AT 18, Steinapol VSL, and Emulphor NPS 25.

The surface-active substance is commonly used in amounts of from 0.1 to10% by weight, based on the monomers to be polymerized.

Water-soluble initiators for the emulsion polymerization are, forexample, ammonium salts and alkali metal salts of peroxodisulfuric acid,e.g., sodium peroxodisulfate, hydrogen peroxide or organic peroxides,e.g., tert-butyl hydroperoxide.

Also suitable are what are known as reduction-oxidation (redox)initiator systems.

The redox initiator systems are composed of at least one usuallyinorganic reducing agent and an organic or inorganic oxidizing agent.

The oxidation component comprises, for example, the emulsionpolymerization initiators already mentioned above.

The reduction component comprises, for example, alkali metal salts ofsulfurous acid, such as sodium sulfite, sodium hydrogen sulfite, alkalimetal salts of disulfurous acid such as sodium disulfite, bisulfiteaddition compounds with aliphatic aldehydes and ketones, such as acetonebisulfite or reducing agents such as hydroxymethanesulfinic acid and itssalts, or ascorbic acid. The redox initiator systems may be usedtogether with soluble metal compounds whose metallic component is ableto exist in a plurality of valence states.

Customary redox initiator systems are, for example, ascorbic acid/iron(II) sulfate/sodium peroxodisulfate, tert-butyl hydroperoxide/sodiumdisulfite, and tert-butyl hydroperoxide/sodium hydroxymethanesulfinate.The individual components, e.g., the reducing component, may also bemixtures, e.g., a mixture of sodium hydroxymethanesulfonate and sodiumdisulfite.

These compounds are normally employed in the form of aqueous solutions,the lower concentration being determined by the amount of water that isacceptable in the dispersion and the upper concentration by thesolubility of the respective compound in water. In general theconcentration is from 0.1 to 30% by weight, preferably from 0.5 to 20%by weight, with particular preference from 1.0 to 10% by weight, basedon the solution.

The amount of initiators is generally from 0.1 to 10% by weight,preferably from 0.5 to 5% by weight, based on the monomers to bepolymerized. It is also possible to use two or more different initiatorsfor the emulsion polymerization.

In the polymerization it is possible to use regulators in amounts, forexample, of from 0 to 0.8 part by weight, based on 100 parts by weightof the monomers to be polymerized, the function of these regulatorsbeing to lower the molecular mass. Examples of suitable compounds arethose containing a thiol group, such as tert-butyl mercaptan,ethylhexylacrylic thioglycolate, mercaptoethanol,mercaptopropyltrimethoxysilane or tert-dodecyl mercaptan.

The emulsion polymerization takes place in general at from 20 to 130°C., preferably from 50 to 90° C. The polymerization medium may consisteither of water alone or else of mixtures of water and water-miscibleliquids such as methanol. It is preferred to use water alone. Theemulsion polymerization may be conducted either as a batch process or inthe form of a feed process, which includes staged or gradientprocedures. Preference is given to the feed process, in which a portionof the polymerization mixture is introduced as an initial charge, heatedto the polymerization temperature and partly polymerized, after whichthe remainder of the polymerization mixture is supplied to thepolymerization zone continuously, in stages or under a concentrationgradient, usually by way of two or more spatially separate feed streams,of which one or more contain the monomers in neat or emulsified form,during which the polymerization is maintained. In the polymerization itis also possible to include a polymer seed in the initial charge inorder, for example, to set the particle size more effectively.

The manner in which the initiator is added to the polymerization vesselin the course of the free-radical aqueous emulsion polymerization isknown to the skilled worker. It may either be included in its entiretyin the initial charge to the polymerization vessel or else insertedcontinuously or in stages at the rate at which it is consumed in thecourse of the free-radical aqueous emulsion polymerization. In eachindividual case this will depend both on the chemical nature of theinitiator system and on the polymerization temperature. Preferably, oneportion is included in the initial charge and the remainder is suppliedto the polymerization zone in accordance with the rate of consumption.

In order to remove the residual monomers, it is also common to addinitiator after the end of the emulsion polymerization proper, i.e.,after a monomer conversion of at least 95%.

In the case of the feed process, the individual components may be addedto the reactor from the top, through the side, or from below, throughthe reactor floor.

In the emulsion polymerization, aqueous dispersions of the polymer areobtained with solids contents of generally from 15 to 75% by weight,preferably from 40 to 75% by weight.

For a high space/time yield of the reactor, dispersions having a veryhigh solids content are preferred. In order to be able to achieve solidscontents >60% by weight, a bimodal or polymodal particle size should beestablished, since otherwise the viscosity becomes too high and thedispersion can no longer be handled. Producing a new particle generationcan be effected, for example, by adding seed (EP-A 81083), by addingexcess amounts of emulsifier, or by adding miniemulsions. A furtheradvantage associated with the low viscosity at high solids content isthe improved coating behavior at high solids contents. One or more newparticle generations may be produced at any point in time. This point intime is guided by the particle size distribution which is aimed at for alow viscosity.

The polymer prepared in this way is used preferably in the form of itsaqueous dispersion.

The glass transition temperature of the polymeric binder, or of theemulsion polymer, is preferably from −60 to +150° C., with particularpreference from −50 to +140° C., and with very particular preferencefrom −4 to +120° C.

The glass transition temperature may be determined in accordance withcustomary methods such as differential thermal analysis or differentialscanning calorimetry (cf., e.g., ASTM 3418/82, midpoint temperature).

Besides the emulsion polymer (EP), the aqueous polymer dispersioncomprises monofunctional or polyfunctional epoxide compounds ascuratives. In this context use is made preferably of epoxide compoundshaving a functionality, in particular, of two or three, examples beingthe corresponding glycidyl ethers. Particularly suitable epoxidecompounds include bisphenol A diglycidyl ethers of the formula (II)

where n is from 0 to 15.

The corresponding bisphenol A diglycidyl ether derivative where n is 0is sold, for example, as a commercial product under the name Epicote®828 by Shell.

Further particularly suitable epoxide compounds include butanedioldiglycidyl ether, pentaerythritol triglycidyl ether, neopentyl glycoldiglycidyl ether, and hexanediol diglycidyl ether. It is also possibleto use water-dispersible epoxide compounds.

Considered generally, the epoxide compounds which can be used includearomatic glycidyl compounds such as the bisphenols A of the formula (II)or their bromo derivatives, and also phenol novolak glycidyl ethers orcresol novolak glycidyl ethers, bisphenol F diglycidyl ethers, glyoxaltetraphenol tetraglycidyl ethers, N,N-diglycidylaniline, p-aminophenoltriglycide, and 4,4′-diaminodiphenylmethane tetraglycide.

Further suitable epoxide compounds include cycloaliphatic glycidylcompounds such as, for example, diglycidyl tetrahydrophthalate,diglycidyl hexahydrophthalate or hydrogenated bisphenol A diglycidylether or heterocyclic glycidyl compounds such as triglycidylisocyanurate and also triglycidyl-bis-hydantoin.

Further epoxide compounds which can be used include cycloaliphatic epoxyresins such as 3,4-epoxycyclohexylmethyl3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl) adipateor 3-(3′,4′-epoxycyclohexyl)-2,4-dioxaspiro[5,5]-8,9-epoxyundecane, andaliphatic epoxy resins such as 1,4-butanediol diglycidyl ether orpolypropylene glycol-425 diglycidyl ether.

The epoxide compounds used in accordance with the invention may bestirred into the aqueous polymer dispersion either before or during thepolymerization of the constituent monomers of the emulsion polymer, andalso after the end of this polymerization. The stirred incorporation ofthe epoxide compounds may be carried out at temperatures from 10 to 100°C., in particular at temperatures from 10 to 50° C. They are preferablyemployed as curatives in the liquid state.

The amount of the monofunctional or polyfunctional epoxide compounds inthe solids fraction of the binder of the invention, i.e., based on 100parts by weight of the sum of the emulsion polymer and the acid polymer(EP and SP), is preferably from 0.1 to 50 parts by weight, in particularfrom 0.2 to 30 parts by weight, with particular preference from 0.5 to25 parts by weight.

As curative it is possible to use not only individual but also mixturesof different monofunctional or polyfunctional epoxide compounds. Epoxidecompounds of this kind are available commercially.

The aqueous polymer dispersion also includes the acid polymer SP definedat the outset.

SP is a free-radically polymerized polymer composed of from 5 to 100% byweight, preferably from 20 to 100% by weight, with particular preferencefrom 40 to 100% by weight, of an ethylenically unsaturated acid or anethylenically unsaturated acid anhydride.

Mention may be made in particular of acrylic acid or methacrylic acid,maleic acid, fumaric acid, itaconic acid, and maleic anhydride.

With particular preference, SP contains acid anhydrides, e.g., maleicanhydride, or dicarboxylic acids which are able to form anhydrides, e.g.maleic acid.

The polymers SP contain in particular from 5 to 50% by weight,preferably from 10 to 40% by weight, of the last-mentioned dicarboxylicacids or acid anhydrides. The other ethylenically unsaturated compoundsof which the polymer is composed preferably comprise acrylic acid ormethacrylic acid.

The acids may also in principle be present, and used, in the form ofsalts, e.g., alkali metal salts or ammonium salts. Salts of amines arelikewise suitable.

Furthermore, the polymer may also contain the following monomers, forexample, as structural components:

C₁-C₈ alkyl (meth)acrylates, vinyl esters, vinyl ethers, olefins, vinylhalides, unsaturated nitriles, etc.

The aqueous polymer dispersion may further comprise a polyol ascrosslinking agent for the polymer SP.

The compounds in question are preferably low molecular mass compoundshaving a molar weight of below 2000 g/mol, in particular below 1000g/mol.

Preference is given to polyols having a functionality of from 2 to 5,such as glycerol, trimethylolpropane, etc.

Alkanolamines are particularly preferred. Mention may be made inparticular of diethanolamine and triethanolamine. Alkanolamines usedwith further preference are known, inter alia, from EP-A 902796, whosedisclosure content in this respect is part of the present invention'sdescription.

Particularly suitable polymers SP are those as described in EP-A 882074.

SP and polyol crosslinker are preferably used in a ratio to one anotherwhich is such that the molar ratio of carboxyl groups to hydroxyl groupsis from 20:1 to 1:1, more preferably from 8:1 to 5:1, and withparticular preference from 5:1 to 1.7:1 (anhydride groups are in thiscase counted as two carboxyl groups).

The acid polymer and the polyol may be added to the aqueous dispersionat any desired point in time.

The aqueous polymer dispersion may comprise phosphorous reactionaccelerators; preferably, however, it contains no such compounds.

In one particular embodiment, the emulsion polymer is prepared in thepresence of at least a portion of the acid polymer SP. In this case SPis preferably composed of

-   -   from 50 to 99.5% by weight of at least one ethylenically        unsaturated monocarboxylic or dicarboxylic acid or a        dicarboxylic anhydride,    -   from 0.5 to 50% by weight of at least one ethylenically        unsaturated compound selected from the esters of ethylenically        unsaturated monocarboxylic acids and the monoesters and diesters        of ethylenically unsaturated dicarboxylic acids with an amine        containing at least one hydroxyl group, and    -   up to 20% by weight of at least one further monomer.

With particular preference, the emulsion polymerization takes place inthe presence of at least 30% by weight, in particular at least 50% byweight, with very particular preference 100% by weight, of the totalamount of SP.

The polymer SP contains from 50 to 99.5% by weight, preferably from 70to 99% by weight, of incorporated structural elements derived from atleast one ethylenically unsaturated monocarboxylic or dicarboxylic acid.Within the polymer, if desired, these acids may also be present in wholeor in part in the form of a salt. The acidic form is preferred.

Preferably, SP has a solubility in water (at 25° C.) of more than 10g/l.

Preferred carboxylic acids are C₃ to C₁₀ monocarboxylic acids and C₄ toC₈ dicarboxylic acids, especially acrylic acid, methacrylic acid,crotonic acid, fumaric acid, maleic acid, 2-methylmaleic acid and/oritaconic acid. Particular preference is given to acrylic acid,methacrylic acid, maleic acid, and mixtures thereof. In the preparationof the polymer SP it is of course also possible, instead of or togetherwith the acids, to use their anhydrides, such as maleic anhydride,acrylic anhydride or methacrylic anhydride.

The polymer SP further contains in copolymerized form from 0.5 to 50% byweight, preferably from 1 to 30% by weight, of at least oneethylenically unsaturated compound selected from the esters ofethylenically unsaturated monocarboxylic acids and the monoesters anddiesters of ethylenically unsaturated dicarboxylic acids with at leastone hydroxyl-containing amine.

The polymer SP is preferably present in the form of a comb polymer withcovalently bonded amine sidechains.

Monocarboxylic acids suitable for the esters are the abovementioned C₃to C₁₀ monocarboxylic acids, especially acrylic acid, methacrylic acid,crotonic acid, and mixtures thereof.

Dicarboxylic acids suitable for the monoesters and diesters are theabovementioned C₄ to C₈ dicarboxylic acids, especially fumaric acid,maleic acid, 2-methylmaleic acid, itaconic acid, and mixtures thereof.

The amine containing at least one hydroxyl group is preferably selectedfrom secondary and tertiary amines having at least a C₆ to C₂₂ alkyl, C₆to C₂₂ alkenyl, aryl-C₆ to C₂₂ alkyl or aryl-C₆ to C₂₂ alkenyl radical,where the alkenyl group may contain 1, 2 or 3 nonadjacent double bonds.

The amine is preferably hydroxyalkylated and/or alkoxylated. Alkoxylatedamines preferably have one or two alkylene oxide radicals with terminalhydroxyl groups. The alkylene oxide radicals preferably each have from 1to 100, more preferably each from 1 to 50, identical or differentalkylene oxide units, randomly distributed or in the form of blocks.Preferred alkylene oxides are ethylene oxide, propylene oxide and/orbutylene oxide. Ethylene oxide is particularly preferred.

The polymer SP preferably incorporates an unsaturated compound based onan amine component containing at least one amine of the formulaR^(c)NR^(a)R^(b)where

-   R^(c) is C₆ to C₂₂ alkyl, C₆ to C₂₂ alkenyl, aryl-C₆-C₂₂ alkyl or    aryl-C₆-C₂₂ alkenyl, it being possible for the alkenyl radical to    have 1, 2 or 3 nonadjacent double bonds,-   R^(a) is hydroxy-C₁-C₆ alkyl or a radical of the formula (III)    —(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)—H  (III)    -   where    -   in the formula (III) the sequence of the alkylene oxide units is        arbitrary and x and y independently of one another are integers        from 0 to 100, preferably from 0 to 50, the sum of x and y being        >1,-   R^(b) is hydrogen, C₁ to C₂₂ alkyl, hydroxy-C₁-C₆ alkyl, C₆ to C₂₂    alkenyl, aryl-C₆-C₂₂ alkyl, aryl-C₆-C₂₂ alkenyl or C₅ to C₈    cycloalkyl, it being possible for the alkenyl radical to have 1, 2    or 3 nonadjacent double bonds,    -   or R^(b) is a radical of the formula (IV)        —(CH₂CH₂O)_(v)(CH₂CH(CH₃)O)_(w)—H  (IV)    -   where    -   in the formula (IV) the sequence of the alkylene oxide units is        arbitrary and v and w independently of one another are integers        from 0 to 100, preferably from 0 to 50.

Preferably R^(c) is C₈ to C₂₀ alkyl or C₈ to C₂₀ alkenyl, it beingpossible for the alkenyl radical to have 1, 2 or 3 nonadjacent doublebonds. R^(c) is preferably the hydrocarbon radical of a saturated ormono- or polyunsaturated fatty acid. Preferred radicals R^(c) are, forexample, n-octyl, ethylhexyl, undecyl, lauryl, tridecyl, myristyl,pentadecyl, palmityl, margarinyl, stearyl, palmitoleinyl, oleyl andlinolyl.

With particular preference, the amine component comprises an alkoxylatedfatty amine or an alkoxylated fatty amine mixture. The ethoxylates areparticularly preferred. Use is made in particular of alkoxylates ofamines based on naturally occurring fatty acids, such as tallow fattyamines, for example, which contain predominantly saturated andunsaturated C₁₄, C₁₆ and C₁₈ alkylamines, or cocoamines, containingsaturated, mono- and diunsaturated C₆-C₂₂, preferably C₁₂-C₁₄,alkylamines. Amine mixtures suitable for alkoxylation are, for example,various Armeen® grades from Akzo or Noram® grades from Ceca.

Examples of suitable commercially available alkoxylated amines are theNoramox® grades from Ceca, preferably ethoxylated oleyl-amines, such asNoramox® 05 (5 EO units), and the products from BASF AG marketed underthe brand name Lutensol®FA.

Copolymerization of the abovementioned esters, monoesters and diestersgenerally brings about pronounced stabilization of a polymer dispersionprepared in the presence of SP. The binders of the invention reliablyretain their colloidal stability of the latex particles on dilution withwater or dilute electrolytes or surfactant solutions.

The esterification for preparing the above-described esters, monoestersand diesters takes place in accordance with customary techniques knownto the skilled worker. To prepare esters of unsaturated monocarboxylicacids, the free acids or suitable derivatives, such as anhydrides,halides, e.g., chlorides, and (C₁ to C₄) alkyl esters may be used. Thepreparation of monoesters of unsaturated dicarboxylic acids takes placepreferably starting from the corresponding dicarboxylic anhydrides. Thereaction is preferably effected in the presence of a catalyst, such as adialkyl titanate or an acid, such as sulfuric acid, toluenesulfonic acidor methanesulfonic acid, for example. The reaction takes place generallyat reaction temperatures from 60 to 200° C. In accordance with oneappropriate embodiment, the reaction takes place in the presence of aninert gas, such as nitrogen. Water formed during the reaction may beremoved from the reaction mixture by means of appropriate measures, suchas distillation. The reaction may take place if desired in the presenceof customary polymerization inhibitors. Essentially, the esterificationreaction may be conducted to completion or just to a partial conversion.If desired, one of the ester components, preferably thehydroxyl-containing amine, may be used in excess. The extent ofesterification may be determined by means of infrared spectroscopy.

In one preferred embodiment, the unsaturated esters, monoesters ordiesters are prepared and further reacted to the polymers SP withoutisolation of the esters, the reactions preferably taking place insuccession in the same reaction vessel.

To prepare the polymers SP it is preferred to use a reaction product ofa dicarboxylic anhydride, preferably maleic anhydride, and one of theabove-described hydroxyl-containing amines.

In addition to the carboxylic acid and the ester, monoester and/ordiester constituents, the polymer SP may also contain in copolymerizedform from 0 to 20% by weight, preferably from 0.1 to 10% by weight, ofother monomers. Monomers which may be used are the monomers specified inconnection with polymer A1, particular preference being given tovinylaromatic compounds, such as styrene, olefins, ethylene for example,or (meth)acrylic esters such as methyl (meth)acrylate, ethyl(meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, andmixtures thereof.

The polymers SP are prepared preferably by free-radical polymerizationin bulk or in solution. Examples of suitable solvents for the solventpolymerization are water, water-miscible organic solvents such asalcohols and ketones, examples being methanol, ethanol, n-propanol,isopropanol, n-butanol, acetone, methyl ethyl ketone, etc., and mixturesthereof. Examples of suitable polymerization initiators are peroxides,hydroperoxides, peroxodisulfates, percarbonates, peroxo esters, hydrogenperoxide and azo compounds, as described in more detail above for thepreparation of the polymer dispersions of the invention. If desired, thepolymers SP may be prepared separately and isolated and/or purified by aconventional method. Preferably, the polymers SP are prepared directlybefore the preparation of the polymer dispersions of the invention andthey are used without isolation for the dispersion polymerization.

The polymers SP may advantageously also be prepared by means ofpolymer-analogous reaction. For this purpose a polymer incorporatingfrom 80 to 100% by weight of at least one ethylenically unsaturatedmono- and/or dicarboxylic acid and from 0 to 20% by weight of theabovementioned other polymers may be reacted with at least onehydroxyl-containing amine.

The weight ratio of polymer EP to polymer SP, based on solids, ispreferably in the range from 7:1 to 1:7, in particular from 3:1 to 1:3.

In addition to the polymers EP and SP and the epoxide compounds, theaqueus polymer dispersion may further comprise from 0 to 50% by weight,preferably from 0.1 to 40% by weight, based on the polymer SP, of atleast one surface-active, alkoxylated, preferably ethoxylated (EO) orpropoxylated (PO), alkylamine.

Preferred alkylamines are the alkylamines of the formulaR^(c)NR^(a)R^(b), as defined above, which are also present in thepolymer SP, particular preference being given to alkylamines of theformula

where R is an alkyl, alkenyl or alkylvinyl radical having at least 6carbon atoms and m and n independently of one another are ≧1. Preferredradicals R have 8 to 22 carbon atoms.

The alkoxylated alkylamines, present in the polymer SP, and theadditional alkylamine crosslinkers may be identical or differentcompounds.

Particularly preferred compositions of the polymer dispersions contain

-   a) from 70 to 30% by weight of polymer EP,-   b) from 30 to 70% by weight of polymer SP, and, if desired,-   c) from 0 to 10% by weight of surface-active alkoxylated alkylamine,-   d) from 0 to 20% by weight of polyol crosslinker,-   e) from 0 to 5% by weight of reaction accelerant (in particular, no    reaction accelerant), and additionally,    based on the weight sum of a) to e), the above-indicated amount of    the monofunctional or polyfunctional epoxide compounds.

Further to the abovementioned constituents, customary additives may beadded depending on the intended application. The polymer dispersion andthe polymer dispersion comprising further additives are referred tocollectively below as “composition”.

The additional components that may be present in the composition aregenerally added after the end of the emulsion polymerization.

Furthermore, the compositions may include customary additives, dependingon their intended application. Examples which may be present includebactericides or fungicides. Furthermore, they may includehydrophobicizing agents in order to increase the water resistance of thetreated substrates. Suitable hydrophobicizing agents are customaryaqueous paraffin dispersions or silicones. In addition, the compositionsmay comprise wetting agents, thickeners, plasticizers, retention agents,pigments, and fillers.

Finally, the compositions of the invention may comprise customary flameretardants, such as aluminum silicates, aluminum hydroxides, boratesand/or phosphates, for example.

The compositions may also be used as blends with other binders, such asurea-formaldehyde resins, melamine-formaldehyde resins orphenol-formaldehyde resins, for example.

The compositions are preferably formaldehyde-free. Formaldehyde-freedenotes that the compositions contain no substantial amounts offormaldehyde and also that no substantial amounts of formaldehyde arereleased in the course of drying and/or curing. In general, thecompositions contain <100 ppm formaldehyde. They permit the productionof moldings with a short curing time, and give the moldings excellentmechanical properties.

Prior to their use, the compositions are essentially uncrosslinked andare therefore thermoplastic. If required, however, a low level ofprecrosslinking of the polymer EP may be established, by using, forexample, monomers having two or more polymerizable groups.

The polymer dispersion or composition may be used as binders for fibrousand particulate substrates, such as, for example, wood chips, woodfibers, textile fibers, glass fibers, mineral fibers or natural fiberssuch as jute, flax, hemp or sisal, and also cork chips or sand. Curingthereof gives shaped parts having a high mechanical strength, which alsoretain their dimensional stability under humid conditions. Heat curingis preferred. The curing temperatures are generally from 80 to 250° C.,preferably from 100 to 200° C.

On heating, the water in the composition evaporates and the compositioncures (hardens). These processes may proceed simultaneously or insuccession. By curing in this context is meant the chemical alterationof the composition; for example, crosslinking by formation of covalentbonds between the different constituents of the compositions, formationof ionic interactions and clusters, and formation of hydrogen bonds.Curing may also be accompanied by physical changes within the binder,such as phase rearrangements or phase inversions, for example. Anadvantage of the heat-curable binder of the invention is that it may becured at comparatively low temperatures. The duration and temperature ofheating influence the degree of cure. The quality of crosslinking may bedetermined from the leaching loss in water at room temperature (RT).This gives the so-called gel content of the polymer. The gel content ofpolymer films after 30-minute crosslinking at 130° C. is at least 50%,preferably at least 70%. The degree of crosslinking brought about by theepoxide may be determined by, inter alia, infrared spectroscopy.

Curing may also take place in two or more stages. For example, in afirst step the curing temperature and time may be chosen such that thedegree of curing attained is low, and substantially complete curingtakes place in a second step. This second step may take place in spatialand temporal separation from the first step. By this means, for example,it becomes possible to use the heat-curable binder of the invention toproduce semifinished goods which are impregnated with binder and thenare shaped and cured at another location.

The invention further provides for the use of the heat-curable bindersbased on an aqueous polymer dispersion as binders for moldings andnonwovens formed from fibrous or particulate materials with subsequentcuring.

Such moldings preferably have a density of from 0.2 to 1.4 g/cm³ at 23°C.

Particularly suitable moldings are sheets and shaped parts having aparticular contour. Their thickness is generally at least 1 mm,preferably at least 2 mm, and their surface area is typically from 200to 200,000 cm². Consideration may be given, in particular, to woodfiberboards and chipboards, cork boards, cork blocks and cork molds,insulant boards and insulant rolls made, for example, from mineralfibers and glass fibers, interior automotive parts, such as interiordoor trim, dashboards, and parcel shelves.

The amount by weight of the binder used is generally from 0.5 to 40% byweight, preferably from 1 to 30% by weight (binder solids), based on thesubstrate (fibers, slivers or chips) from which the molding or nonwovenis then formed.

The fibers, slivers or chips can be coated directly with the binder ormixed with the aqueous binder. The viscosity of the aqueous binder ispreferably adjusted to from 10 to 4000, with particular preference tofrom 30 to 2000 mPas (DIN 53019, rotational viscometer at 250 s⁻¹).

The mixture of fibers, slivers and chips and the binder can be subjectedto initial drying at temperatures, for example, of from 10 to 150° C.and then to compression molding to form the moldings at temperatures,for example, of from 80 to 250° C., preferably from 100 to 200° C. andunder pressures of generally from 2 to 1000 bar, preferably from 10 to750 bar, with particular preference from 200 to 500 bar.

The binders are particularly suitable for producing woodbase materialssuch as wood chipboards and wood fiberboards (cf. Ullmanns Encyclopädieder technischen Chemie, 4^(th) edition 1976, volume 12, pp. 709-727),which can be produced by gluing disintegrated wood, such as wood chipsand wood fibers, for example. The water resistance of woodbase materialscan be enhanced by adding to the binder a customary commercial aqueousparaffin dispersion or other hydrophobicizing agents, or adding saidhydrophobicizing agents beforehand or subsequently to the fibers,slivers or chips.

Chipboard production is widely known and is described, for example, inH. J. Deppe, K. Ernst Taschenbuch der Spanplattentechnik, 2^(nd)edition, verlag Leinfelden 1982.

It is preferred to use chips whose average size is from 0.1 to 4 mm, inparticular from 0.2 to 2 mm, and which contain less than 6% by weight ofwater. However, it is also possible to use considerably coarser chipsand those with a higher moisture content. The binder is applied withgreat uniformity to the wood chips, the weight ratio of binder solids towood chips preferably being from 0.02:1 to 0.3:1. Uniform distributioncan be achieved, for example, spraying the binder in finely divided formonto the chips.

The glued wood chips are then scattered out to form a layer with ahighly uniform surface, the thickness of the layer being guided by thedesired thickness of the finished chipboard. The scattered layer ispressed at a temperature of from 100 to 250° C., for example, preferablyfrom 120 to 225° C., by applying pressures of usually from 10 to 750bar, to form a board. The required press times may vary within a widerange and are generally from 15 seconds to 30 minutes.

The wood fibers of appropriate quality required to produce mediumdensity fiberboard (MDF) panels from the binders can be produced frombarkless wood chips by milling in special mills or refiners attemperatures of about 180° C.

For gluing, the wood fibers are generally swirled up in a stream of airand the binder is introduced through nozzles into the resultant fiberstream (blow-line process). The ratio of wood fiber to binder based onthe dry-matter content or solids content is usually from 40:1 to 2:1,preferably from 20:1 to 4:1. The glued fibers are dried in the fiberstream at temperatures of, for example, from 130 to 180° C., scatteredout to form a fiber web, and pressed under pressures of from 10 to 50bar to form boards or moldings.

Alternatively, as described for example in DE-A-2 417 243, the gluedwood fibers can be processed to a transportable fiber mat. Thisintermediate can then be processed further to boards or shaped parts,such as door interior trim panels of motor vehicles, for example, in asecond, temporally and spatially separate step.

Other natural fiber substances as well, such as sisal, jute, hemp, flax,coconut, banana and other natural fibers, can be processed with thebinders to form boards and shaped parts. The natural fiber materials canalso be used in mixtures with plastic fibers, such as polypropylene,polyethylene, polyester, polyamides or polyacrylonitrile. In this casethe plastic fibers may also function as cobinders in addition to thebinder of the invention. The proportion of plastic fibers in this caseis preferably less than 50% by weight, in particular less than 30% byweight and, with very particular preference, less than 10% by weight,based on all chips, slivers or fibers. The fibers can be processed bythe method used for the wood fiberboards. Alternatively, preformednatural fiber mats can be impregnated with the binders, with or withoutthe addition of a wetting auxiliary. The impregnated mats, in thebinder-moist or predried state, are then pressed at temperatures from100 to 250° C. under pressures of from 10 to 100 bar, for example, toform boards or shaped parts.

The substrates impregnated with the binders preferably have a residualmoisture content on pressing of from 3 to 20% by weight, based on thesubstrate to be bound.

The moldings obtained feature low water absorption, little increase inthickness (swelling) after storage in water, and good strength, and areformaldehyde-free.

In addition, the compositions can be used as binders for coatingmaterials and impregnating materials for boards made of organic and/orinorganic fibers, nonfibrous mineral fillers, and starch and/or aqueouspolymer dispersions. The coating and impregnating materials impart ahigh flexural modulus to the boards. The production of such boards isknown.

Boards of this kind are commonly used as soundproofing panels. Thethickness of the panels is usually within the range from about 5 to 30mm, preferably in the range from 10 to 25 mm. The edge length of thesquare or rectangular panels is usually in the range from 200 to 2000mm.

In addition, the compositions may include the auxiliaries customary incoating and impregnating technology. Examples of such auxiliaries arefinely divided inert fillers, such as aluminum silicates, quartz,precipitated or pyrogenic silica, light and heavy spar, talc, dolomiteor calcium carbonate; color pigments, such as titanium white, zincwhite, black iron oxide, etc., foam inhibitors, such as modifieddimethylpolysiloxanes, and adhesion promoters, and also preservatives.

The components of the composition are generally present in the coatingmaterial in an amount of from 1 to 65% by weight. The proportion of theinert fillers is generally from 0 to 85% by weight, the proportion ofwater being at least 10% by weight.

The compositions are employed in a customary manner by application to asubstrate, for example, by spraying, rolling, pouring or impregnating.The amounts applied, based on the dry-matter content of the composition,are generally from 2 to 100 g/m².

The amounts of additives to be used are known to the skilled worker andare guided in each individual case by the desired properties and theintended application.

The compositions can also be used as binders for insulating materialsmade from inorganic fibers, such as mineral fibers and glass fibers.Insulating materials of this kind are produced industrially by spinningmelts of the corresponding mineral raw materials; see U.S. Pat. No.2,550,465, U.S. Pat. No. 2,604,427, U.S. Pat. No. 2,830,648, EP-A-354913 and EP-A-567 480. The composition is then sprayed onto the freshlyproduced, still hot inorganic fibers. The water then largely evaporatesand the composition remains, in essentially uncured form, adhering as aviscous mass to the fibers. A continuous, binder-containing fiber matproduced in this way is transported on by means of appropriate conveyorbelts through a curing oven. In the oven, the mat cures at temperaturesin the range from about 100 to 200° C. to form a rigid matrix. Aftercuring, the mats of insulating material are processed appropriately.

The predominant fraction of the mineral fibers or glass fibers used inthe insulating materials has a diameter in the range from 0.5 to 20 μmand a length in the range from 0.5 to 10 cm.

The binders of the invention may be used, among other things, in theproduction of filter papers for air filters and oil filters. They mayalso be used as components of decorative papers.

The compositions are further suitable as binders for fiber webs.

Examples of fiber webs that may be mentioned are webs of cellulose,cellulose acetate, esters and ethers of cellulose, cotton, hemp, animalfibers, such as wool or hair, and, in particular, webs of synthetic orinorganic fibers, examples being aramid, carbon, polyacrylonitrile,polyester, mineral, PVC, or glass fibers.

In the case of use as binders for fiber webs, the compositions mayinclude, for example, the following additives: silicates, silicones,boron compounds, lubricants, wetting agents.

Preference is given to glass fiber webs. The unbonded fiber webs(untreated fiber webs), especially of glass fibers, are bound, i.e.,consolidated, by the binder of the invention.

For this purpose the binder is applied to the untreated fiber web bymeans, for example, of coating, impregnating or soaking preferably in aweight ratio of fiber to binder (solids) of from 10:1 to 1:1, withparticular preference from 6:1 to 3:1.

In this case the binder is used preferably in the form of a dilutedaqueous composition containing 95 to 40% by weight of water.

Application of the binder to the untreated fiber web is generallyfollowed by drying and crosslinking at, preferably, from 100 to 400° C.,in particular from 130 to 280° C., with very particular preference from130 to 230° C., over a period of preferably from 10 seconds to 10minutes, in particular from 10 seconds to 3 minutes.

The bonded fiber web obtained has high strength in the dry and wetstates. In particular, the binders of the invention permit short dryingtimes and also low drying temperatures. They may also be dried to asemifinished state allowing later processing.

The bonded fiber webs, especially glass fiber webs, are suitable for useas or in roofing membranes, as base materials for wallpapers, or asinliners or base material for floor coverings made, for example, fromPVC.

For use as roofing membranes, the bonded fiber webs are generally coatedwith bitumen.

The aqueous compositions can also be used to produce foamed boards ormoldings. For this purpose the water present in the composition is firstof all removed down to a level of <20% by weight at temperatures of<100° C. The viscous composition thus obtained is then foamed attemperatures >100° C., preferably from 120 to 300° C. Examples ofblowing agents which can be used are the residual water still present inthe mixture and/or the gaseous reaction products that form in the courseof the curing reaction. However, commercially customary blowing agentscan also be added. The resultant crosslinked polymer foams can be used,for example, for heat insulation and for soundproofing.

The compositions can also be used to produce laminates, for decorativeapplications, for example, by impregnating paper and then carrying outgentle drying, in accordance with the known processes. In a second step,these laminates are laminated onto the substrate to be coated, underpressure and with heat, the conditions being chosen such that curing ofthe binder takes place.

In addition, the compositions can be used to produce sandpaper and otherabrasives by the production techniques customarily carried out withphenolic resin binders. In the production of sandpapers, a layer of thebinders of the invention is first of all applied (judiciously 10 g/m²)as base binder to an appropriate backing paper. The desired amount ofparticulate abrasive, for example, silicon carbide, corundum, etc., isscattered into the wet base binder. After initial drying, a bindertopcoat is applied (e.g., 5 g/m²). The paper coated in this way is thencured by heating at 170° C. for another 5 minutes.

The hardness and flexibility of the composition may be adjusted to thedesired level by way of the composition of the polymer SP.

The compositions are suitable, furthermore, as formaldehyde-free sandbinders for producing casting molds and cores for metal castingaccording to conventional thermal hardening processes (E. Flemming, W.Tilch, Formstoffe und Formverfahren, Dt. Verlag für Grundstoffindustrie,Stuttgart, 1993).

They are also suitable as binders for mold insulating boards.

The heat-curable binders of the invention, based on an aqueous polymerdispersion, are distinguished, inter alia, by substantially reducedwater absorption and solvent absorption and also by substantiallydecreased leaching losses. The moldings obtained using the binders ofthe invention include among their properties that of high strength. Theprocess, likewise of the invention, for preparing the heat-curablebinders is simple and economic to carry out.

EXAMPLES

The nonlimiting examples which follow illustrate the invention.

Example 1

A) Preparation of the Acid Polymer SP

A pressure reactor with anchor stirrer is charged with 0.55 kg ofdeionized water, 0.36 kg of maleic anhydride, and 0.91 kg of a 40%strength by weight aqueous solution of an ethoxylated oleylamine(average degree of ethoxylation=12, from BASF AG). This initial chargeis heated to 125° C. under a nitrogen atmosphere. On reaching thistemperatures feed stream 1, consisting of 0.75 kg of deionized water and1.00 kg of acrylic acid, is metered in over the course of 4 h, and feedstream 2, consisting of 0.22 kg of deionized water and 0.12 kg of H₂O₂(30% strength by weight), is metered in over the course of 5 h, bothfeeds being introduced at a uniform rate. After the end of feed stream1, a further 0.11 kg of deionized water is added. After the end of thereaction, the mixture is cooled to room temperature. The resultantaqueous polymer solution has a solids content of 43.2%, a pH of 1.7, anda viscosity of 450 mPas. The K value is 13.3.

B) Polymer Dispersions (Emulsion Polymerization in the Presence of theAcid Polymer).

Polymer Dispersion with EP1:

A 4 l glass vessel with anchor stirrer (120 rpm) is charged with 640 gof water, 133.1 g of an aqueous solution of the acid polymer SP (43.2%strength by weight) from Example A and 5.35 g (10%) of feedstream 2, andthis initial charge is heated to 90° C. After 10 minutes, at thistemperature, the remainder of feedstream 1 is metered in over the courseof 3 h and the remainder of feedstream 2 over the course of 3.5 h, thefeedpoints being spatially separate. Subsequently, polymerization iscontinued at this temperature for 30 minutes and the reaction mixture iscooled and blended with feedstream 3. The polymer dispersion prepared inthis way contains 47.3% by weight nonvolatiles and has a pH of 2.7. Theviscosity of the resultant polymer dispersion is 630 mPas (at 250 s⁻¹).Finally, 9 parts by weight of triethanolamine (based on the solidscontent) are added to the dispersion.

Feedstream 1: 185.32 g of water 665.51 g of SP (43.2%) 805.00 g ofstyrene (100%) 287.50 g of MMA (100%)  57.50 g of HEA (100%) Feedstream2:   619 g of deionized water  3.45 g of sodium peroxodisulfateFeedstream 3: 1863.43 g of SP (43.2%)

-   X % by weight of triethanolamine and/or epoxide compound (in    accordance with Tables I to V) (triethanolamine and epoxide compound    are added at different points in time)

In feedstream 1 above,

-   MMA: is methyl methacrylate and-   HEA: is hydroxyethyl acrylate.    C) Determination of Water Absorption (WA) and Leaching Losses (LL)    with Water

The polymer films obtained from B), without and with additives (TEA:triethanolamine; E: Epicote® 828, bisphenol A diglycidyl ether), weredried at room temperature for 3 days and then for a further 3 days at50° C.

To determine the water absorption (WA) and leaching losses (LL), about0.2 to 0.3 g of polymer film was stored in 10 g of water for 24 hours.

The polymer film (Acrodur® D100 from BASF Aktiengesellschaft) wascomposed of 100 parts by weight of SP (made from acrylic acid and maleicanhydride; obtained in section A) and also 70 parts by weight ofstyrene, 25 parts by weight of methyl methacrylate and 5 parts by weightof hydroxyethyl acrylate (obtained in section B).

The results of Example 1 are given in Table I below.

TABLE I TEA E [parts by weight [parts by weight based on binder to basedon binder Sample be formulated] to be formulated] WA [%] LL [%] WA andLL following heat treatment of the polymer film at 80° C. for 30 minutes1 9 0 37.7 17.5 2 9 10 30.8 9.8 WA and LL following heat treatment ofthe polymer film at 130° C. for 30 minutes 1 0 0 33.8 4.9 2 0 10 25.20.9

Example 2

The polymer used was the same acid polymer (SP) as in Example 1.Emulsion polymerization was carried out as in section B of Example 1, inthe presence of the SP with 73.5 parts by weight of ethylhexyl acrylate,21 parts by weight of styrene and 5.5 parts by weight of hydroxyethylacrylate.

The polymer films obtained in this way without and with additives (TEA:triethanolamine; E: Epicote® 828, bisphenol A diglycidyl ether), weredried at room temperature for 3 days and then for a further 3 days at50° C.

To determine the water absorption (WA) and leaching losses (LL), about0.2 to 0.3 g of polymer film was stored in 10 g of water or in 100 g ofacetone for 24 hours.

The polymer film was composed of 100 parts by weight of SP (made fromacrylic acid and maleic anhydride; obtained in section A) and also 73.5parts by weight of ethylhexyl acrylate, 21 parts by weight of styreneand 5.5 parts by weight of hydroxyethyl acrylate.

The results of Example 2 are given in Table II below.

TABLE II TEA E [parts by weight [% by weight based based on binder onbinder to be Sample to be formulated] formulated] WA [%] LL [%] WA andLL without heat treatment 1 0 0 61.2 23.3 2 0 10 55.1 8.4 3 0 20 45.96.2 4 0 30 42.2 6.3 5 9 0 61.1 19.6 6 9 10 37.6 9.6 7 9 20 35.9 8.9 8 930 34.5 7.5 WA and LL following heat treatment of the polymer film at100° C. for 30 minutes 1 0 0 53.9 12.2 2 0 10 41.9 6.3 3 0 20 36.8 4.4 40 30 32 3.7 WA and LL following heat treatment of the polymer film at150° C. for 30 minutes 1 9 0 14.1 1.2 2 9 10 10.3 1.2 3 9 20 7.9 0.7

Example 3

The same acid polymer (SP) and the same (in terms of its monomercomposition) emulsion polymer (EP) as in Example 2 were used.

The polymer films obtained in this way, without and with additives (TEA:triethanolamine, and/or the epoxide compounds indicated in Table III)were heat-treated first at room temperature for 3 days, then at 50° C.for 3 days more, and, where appropriate, for a further 30 minutes at100° C. or at 150° C.

The solvent absorption (SA) and leaching losses (LL) in THF(tetrahydrofuran) were determined by storing about 0.5 g of the polymerfilm in 90 ml of THF for 24 hours. For the LL figure, the polymer filmswere dried at room temperature for 7 days beforehand and then dried to aconstant-weight in a forced air oven at 50° C.

The results of Example 3 are given in Table III below.

TABLE III LL without heat treatment Triethanolamine [parts by weightEpoxide compound based on binder [parts by weight based to be on binderto be Sample formulated] formulated] LL in THF [%] 1 0 0 38.5 2 0 30Epicote 828 12.0 3 9 0 12.2 4 9 30 Epicote 828 3.7 AV following heattreatment at 150° C. Triethanolamine Epoxide compound [parts by weight[parts by weight based on binder to based on binder to Sample beformulated] be formulated] AV in THF [%] 1 9 0 8.0 2 9 30 Epicote 8282.6 3 9 30 Butanediol 0.6 diglycidyl ether 4 9 30 Pentaerythritol 3.4triglycidyl ether 5 9 30 Neopentyl glycol 7.1 diglycidyl ether 6 9 30Hexanediol 5.1 diglycidyl ether Solvent absorption (SA) of THFTriethanolamine Epoxide compound [parts by weight Heat [parts by weightbased on binder treatment based on binder to SA THF Sample to beformulated] at X° C. be formulated] [%] 1 0 RT 0 581 2 0 100 0 414 3 0150 0 202 4 0 RT 30 Epicote 828 344 5 0 100 30 Epicote 828 285 6 0 15030 Epicote 828 87 7 9 100 30 Epicote 828 180 8 9 150 30 Epicote 828 1219 9 100 30 Butanediol 109 diglycidyl ether 10 9 100 30 Pentaerythritol109 triglycidyl ether 11 9 100 30 Neopentyl glycol 145 diglycidyl ether12 9 100 30 Hexanediol 128 diglycidyl ether

Example 4

The polymer dispersion obtained in Example 1 was tested for the bendingstrength (BS) and water absorption (WA) properties it gave to sand testspecimens. The bending strength [N/mm²] was determined after 3 hours ofwater storage at 80° C. The water absorption of the sand test specimenswas measured at the same time, in accordance with the following method:

300 g of quartz sand H34 were mixed with the binder compositions at roomtemperature (5% or 3% by weight of dry binder as per table, based onsand). The moist mixtures are shaped in a corresponding metal mold intotest specimens (Fischer bars) measuring 17×2.3×2.3 cm, which arecompacted and then, after demolding, are cured in a forced air oven for2 hours at temperatures as per the table. Compaction is carried outusing a ram type PRA from Georg Fischer AG. Prior to testing, the barswere stored for 3 hours in water at 80° C. The water absorption of thebars is then measured while they are still wet (in table, WA after WS).

The bending strength (BS) of the Fischer bars thus produced isdetermined in the dry state at 23° C. specimen temperature in a strengthtesting apparatus type PFG with the test device PBV (from Georg Fischer,Schaffhausen/CH) (in table BS after WS).

The results of the tests are given in Table IV below.

TABLE IV Curing temperature 150° C. for 2 hours TEA E [parts by weight[parts by weight based on binder to based on binder to WA Sample beformulated] be formulated] BS* [%]* 1 9 0 25 13.6 2 9 10 85 13.3 3 9 20140 11.7 4 9 30 180 10.1 5 0 30 260 11.5 Curing temperature 170° C. for2 hours TEA E [parts by weight [parts by weight based on binder to basedon binder to WA Probe be formulated] be formulated] BS* [%]* 1 9 0 7513.4 2 0 10 235 13.2 3 9 10 320 9.2

The abbreviations here have the following meanings:

-   TEA: Triethanolamine-   E: Epicote® 828 (bisphenol A diglycidyl ether)

Example 5

The polymer dispersions obtained in Examples 1 and 2 were subjected tothe following boiling test with a view to their suitability as bindersfor cork granules:

92.5% by weight of coarse cork, 7.5% by weight of binder; boiling testafter 3 hours; duration of pressing: 2 hours.

In a Kenwood laboratory mixer, 100 g of dried cork granules (cleaned andground cork, average particle size about 8 mm) and 15 g in each case ofthe 50% strength binder from the cited examples are mixed for 2 minutes.The binder-treated cork particles are introduced without further dryinginto a two-part metal mold and pressed under a pressure of 100 bar for 2hours at a pressing temperature of from 80° C. to 100° C. The metal moldhas internal dimensions of 15×15 mm, with the bottom and die of the moldperforated with dent holes to take off the water vapor that is released.

Specimens measuring 5×5×3 cm are cut from these rigid cork blocks andtheir thickness swell is tested under the conditions indicated above.

The results of the cork block boiling test are given in Table V for thepolymer dispersion from Example 1 and in Table VI for the polymerdispersion from Example 2.

TABLE V TEA E [parts by weight [parts by weight based on binder to basedon binder to Pressing Swell Sample be formulated] be formulated]temperature [%] 1 9 0 80 fell apart 2 9 0 90 fell apart 3 9 0 100 fellapart 4 9 30 80 58 5 9 30 90 30 6 9 30 100 24

TABLE VI TEA E [parts by weight [parts by weight based on binder tobased on binder to Pressing Swell Sample be formulated] be formulated]temperature [%] 1 9 0 80 fell apart 2 9 0 90 fell apart 3 9 0 100 fellapart 4 9 30 80 41 5 9 30 90 23 6 9 30 100 23

In the above tables, abbreviations have the following meanings:

-   TEA: Triethanolamine-   E: Epicote® 828 (bisphenol A diglycidyl ether)

1. A heat-curable binder based on an aqueous polymer dispersion, saidaqueous polymer dispersion comprising: an emulsion polymer (EP) preparedby emulsion polymerization of constituent monomers in an aqueous medium,said constituent monomers comprising principle monomers andcopolymerizable monomers, which, when comprising monomers containingcarboxylic acid groups or carboxylic anhydride groups, the fraction ofsaid monomers containing carboxylic acid groups or carboxylic anhydridegroups being less than 5% by weight of the emulsified polymer that isformed; an acid polymer (SP) composed of 40 to 100% by weight of anethylenically unsaturated monocarboxylic acid, an ethylenicallyunsaturated dicarboxylic acid or an ethylenically unsaturateddicarboxylic anhydride; and a curative comprising monofunctional orpolyfunctional epoxide compounds and further comprising a curativeselected from the group consisting of a polyol having a molecular weightof less than 1000 g/mol and an alkanolamine containing at least twohydroxyl groups.
 2. The heat-curable binder as claimed in claim 1,wherein the monofunctional or polyfunctional epoxide compound isemployed in the liquid state as curative.
 3. The heat-curable binder asclaimed in claim 1, wherein a difunctional or trifunctional epoxidecompound is employed as curative.
 4. The heat-curable binder as claimedin claim 1, wherein the emulsion polymer (EP) is composed of at least40% by weight of a principal monomer selected from the group consistingof C₁ to C₂₀ alkyl (meth)acrylates, vinyl esters of carboxylic acidscontaining up to 20 carbon atoms, vinylaromatics having up to 20 carbonatoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethersof alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbonshaving 2 to 8 carbon atoms and one or two double bonds, and mixtures ofthese monomers.
 5. The heat-curable binder as claimed in claim 4,wherein the emulsion polymer (EP) is comprised additionally of at leastone monomer which contains a carboxylic acid group, a sulfonic acidgroup or a phosphonic acid group; a hydroxyl group containing monomer,phenyloxyethyl glycol mono(meth)acrylate, glycidyl acrylate, glycidylmethacrylate, amino (meth)acrylates or a crosslinking monomer.
 6. Theheat-curable binder as claimed in claim 1, wherein the acid polymer (SP)is comprised of: from 50 to 99.5% by weight of at least oneethylenically unsaturated monocarboxylic acid, ethylenically unsaturateddicarboxylic acid, ethylenically unsaturated dicarboxylic anhydride ormixtures thereof, from 0.5 to 50% by weight of at least oneethylenically unsaturated compound selected from the group consisting ofesters of ethylenically unsaturated monocarboxylic acids and themonoesters and diesters of ethylenically unsaturated dicarboxylic acidswith an amine containing at least one hydroxyl group, and optionally, upto 20% by weight of at least one additional monomer.
 7. The heat-curablebinder as claimed in claim 6, wherein the ethylenically unsaturatedmonocarboxylic acid, ethylenically unsaturated dicarboxylic acid orethylenically unsaturated dicarboxylic anhydride is (meth)acrylic acid,maleic acid, fumaric acid, itaconic acid or maleic anhydride.
 8. Theheat-curable binder as claimed in claim 1, wherein the weight ratio ofthe emulsion polymer (EP) to the acid polymer (SP) based on solids is inthe range from 7:1 to 1:7.
 9. The heat-curable binder as claimed inclaim 1, wherein the epoxy curative is a bisphenol A diglycidyl ether,butanediol diglycidyl ether, pentaerythritol triglycidyl ether,neopentyl glycol diglycidyl ether, or hexanediol diglycidyl ether. 10.The heat-curable binder as claimed in claim 1, wherein the epoxycurative is present in an amount ranging from 0.1 to 50 parts by wtbased on 100 parts by wt of the sum of emulsion polymer (EP) and acidpolymer (SP).
 11. A composite prepared from a fibrous or particulatematerial combined with the heat-curable binder as claimed in claim 1.12. A process for preparing an aqueous polymer dispersion, said processcomprising the sequential steps of: preparing an emulsion polymer (EP)by emulsion polymerization of constituent monomers in an aqueous medium,wherein the emulsion polymerization is performed in the presence of anacid polymer (SP), yielding an aqueous polymer dispersion; and stirringa curative into the aqueous polymer dispersion, wherein the curativecomprises monofunctional or polyfunctional epoxide compounds; whereinthe emulsion polymer (EP) is prepared from principle monomers andcopolymerizable monomers, which, when comprising monomers containingcarboxylic acid groups or carboxylic anhydride groups, the fraction ofsaid monomers containing carboxylic acid groups or carboxylic anhydridegroups being less than 5% by weight of the emulsified polymer that isformed; and wherein the acid polymer (SP) is composed of 40 to 100% byweight of an ethylenically unsaturated monocarboxylic acid, anethylenically unsaturated dicarboxylic acid or an ethylenicallyunsaturated dicarboxylic anhydride.
 13. The process as claimed in claim12, wherein the monofunctional or polyfunctional epoxide compounds areincorporated into the dispersion by stirring at temperatures rangingfrom 10 to 100° C.
 14. The process as claimed in claim 12, wherein themonofunctional or polyfunctional epoxide compounds are further combinedwith a polyol having a molecular weight of less than 1000 g/mol or analkanolamine containing at least two hydroxyl groups.
 15. A process forpreparing an aqueous polymer dispersion, said process comprising:preparing an emulsion polymer (EP) by emulsion polymerization ofconstituent monomers in an aqueous medium, wherein the emulsionpolymerization is performed in the presence of an acid polymer (SP); andwherein the emulsion polymerization is performed while stirring acurative into the aqueous medium; wherein the emulsion polymer (EP) isprepared from principle monomers and copolymerizable monomers, which,when comprising monomers containing carboxylic acid groups or carboxylicanhydride groups, the fraction of said monomers containing carboxylicacid groups or carboxylic anhydride groups being less than 5% by weightof the emulsified polymer that is formed; wherein the acid polymer (SP)is composed of 40 to 100% by weight of an ethylenically unsaturatedmonocarboxylic acid, an ethylenically unsaturated dicarboxylic acid oran ethylenically unsaturated dicarboxylic anhydride; and wherein thecurative comprises monofunctional or polyfunctional epoxide compounds.16. The process as claimed in claim 15, wherein the monofunctional orpolyfunctional epoxide compounds are incorporated into the aqueousmedium by stirring at temperatures ranging from 10 to 100° C.
 17. Theprocess as claimed in claim 15, wherein the monofunctional orpolyfunctional epoxide compounds are further combined with a polyolhaving a molecular weight of less than 1000 g/mol or an alkanolaminecontaining at least two hydroxyl groups.